Several electronic handheld devices are now proposed which make possible to capture digital images. These devices are for instance classical digital cameras, or other devices such as mobile phones or personal digital assistants offering camera capabilities. Such devices are classically equipped with a camera unit and capture means for triggering an image capture, for instance a dedicated key, or, in case of a mobile phone, a track ball or any navigating means. These devices generally further comprise power supplying means, like a rechargeable battery, for delivering power supply to said camera unit, but also to other components in the device, such as a display unit, a keyboard unit, and/or, in the case of a mobile phone, a transmitting/receiving unit.
For some of these additional components, it may be necessary to increase and to regulate the voltage delivered by the battery. This is the case namely for the display backlight driver or for the keyboard backlight driver which belongs respectively to display unit and to keyboard unit. For this purpose of regulation, a DC/DC converter is generally used connected between the power supplying means output and a component power input. The principle of such a DC/DC converter is to take at a high frequency some amount of current on the battery in order to load a capacitor until a predetermined voltage is reached. However, this induces on the voltage outputting the battery some undesirable voltage drops. If an image is captured at this time, this can lead to a degradation of the overall quality of the captured image. This phenomena gets worse if the display backlight driver is connected to the DC/DC converter, and if an image is to be taken in low ambient light conditions. Indeed, in this case, since the display backlight is also used to preview the image, the noise induced by the DC/DC converter will be so important that it will not be possible to get a correct picture.
One solution to this problem is to provide the electronic handheld device with several big capacitors which filter power supplies. However, these capacitors take too much place in a device for which miniaturized size is an important marketing aspect.
Another solution consists in filtering the image once captured. However, this reduces generally the resolution and thus the overall quality of the picture.